Measurement of cross section for $e^{+}{e}^{-}\to {\mathrm{\Xi }}^{-}{\overline{\mathrm{\Xi }}}^{+}$ near threshold at BESIII

The Born cross sections and effective form factors for process $e^{+}{e}^{-}\to {\mathrm{\Xi }}^{-}{\overline{\mathrm{\Xi }}}^{+}$ are measured at eight center-of-mass energies between 2.644 and 3.080 GeV, using a total integrated luminosity of $363.9{\mathrm{pb}}^{-1}$ $e^{+}{e}^{-}$ collision data collected with the BESIII detector at BEPCII. After performing a fit to the Born cross section of $e^{+}{e}^{-}\to {\mathrm{\Xi }}^{-}{\overline{\mathrm{\Xi }}}^{+}$, no significant threshold effect is observed.

Figure 1

Distribution of $M_{\mathrm{\Lambda }{\pi }^{-}}^{\text{recoil}}$ versus $M_{\mathrm{\Lambda }{\pi }^{-}}$ from data. The dashed lines denote the ${\mathrm{\Xi }}^{-}$ signal region.

Figure 2

Fit of the recoil mass spectra of $\mathrm{\Lambda }{\pi }^{-}$ at each energy point. Dots with error bars are data, the solid lines show the fit result, the long dashed lines represent the signal contribution, and the short dashed lines represent the smooth background.

Figure 3

Fit to the measured Born cross section with different assumptions. The dots with the error bars are the measured Born cross sections at c.m. energies between 2.644 and 3.080 GeV. The dash-dotted line denotes the fit results using Eq. (6). The solid line denotes the fit results using Eq. (7). The dashed line denotes the fit results using Eq. (9), The vertical dashed line denotes the production threshold for $e^{+}{e}^{-}\to {\mathrm{\Xi }}^{-}{\overline{\mathrm{\Xi }}}^{+}$.